1. Field of the Invention
This invention relates to a magnetic disk cartridge and more particularly to a structure of a write/protect tab.
2. Description of the Prior Art
An inadvertent erasure prevention tab (hereinafter referred to as a write/protect tab) of a conventional magnetic disk cartridge is slidably disposed at one corner portion in a case and intended to prevent inadvertent eraser of the information on the disk.
An inadvertent erasure prevention mechanism of the conventional magnetic disk cartridge will be described with reference to FIGS. 17 through 23.
The conventional disk cartridge comprises a case 1 and comprises a magnetic disk (not shown) inserted in the case 1. The case 1, as shown in FIG. 17, a pair of case members, i.e., a cover case 2a and a bottom case 2b assembled together. Each of the case members 2a and 2b is provided with a generally C-shaped liner 3, 3 adhered to the inner surface thereof. The inner surfaces of the case members 2a and 2b are also provided with rectangular windows 21, 21 formed between end portions of the liners 3, 3 and adapted to allow a magnetic head (not shown) access to the magnetic disk to record information thereon or reproduce information recorded thereon through the windows 21, 21. Also, one corner portion of the case members 2a and 2b is provided with rectangular peripheral walls 22, 22 which, when the case members 2a and 2b are assembled together, form a tab pocket, as shown in FIGS. 18 through 20, for slidably receiving therein a write/protect tab 4 as shown in FIG. 21.
The write/protect tab 4, as shown in FIG. 21, comprises a body portion 4A, and a pair of arm portions 4B, 4B extending along both sides of the body portion 4A and terminating in projecting portions 4C, 4C projecting outwardly from outer ends of the arm portions 4B, 4B. Most of the arm portions 4B, 4B are formed such that they are gradually dilated outwardly. And owing to rounded projecting portions 22B, 22B, (which will be described afterwards), the projecting portions 4C, 4C at the tips of the arm portions 4B, 4B are more securely encaptured.
Either of the case members 2a, 2b, e.g., bottom case member 2a is provided with two pairs of rounded projecting portions 22B, 22B formed on the opposite inner side wall portions in the rectangular peripheral walls 22 of the case bottom member 2a, i.e., a pair of side wall portions 22 (see FIG. 18) along a sliding direction of the write/protect tab 4 and adapted to receive end portions of the corresponding projecting portions 4C, 4C of the pair of arm portions 4B, 4B. And a pair of curved wall surfaces 22C, 22C are provided between the rounded projecting portions. The write/protect tab 4 is slidably mounted in the tab pocket, as shown in FIG. 18, which is formed by a combination of the corresponding peripheral walls 22, 22 of the case bottom member 2a and case cover member 2b. The pair of projecting portions 4C, 4C are received by the corresponding rounded projecting portions 22B, 22B of the side wall portions 22A, 22A. The thickness of each write/protect tab 4 is greater than the height of each side wall portion 22 as shown in FIG. 22. The tab 4 is received by either of the retaining projecting portions 22B, 22B, to thereby fix the body portion 4A to a closing position (see FIG. 19) or an opening position (see FIG. 20) for an opening 23 (shown in FIG. 18) formed in the peripheral wall 22 of the case cover member 2. As shown in FIG. 20, when the body portion 4A is in the position for opening the opening 23, the tab 4 acts to prevent inadvertent eraser. The numeral 24 denotes a guide opening formed in the peripheral wall of the case bottom member 2 and adapted to guide the inadvertent eraser prevention tab 4 in the tab pocket.
When the magnetic disk cartridge is assembled, the projecting portions 4C, 4C are usually placed between the rounded projecting portions 22B, 22B (see FIG. 18).
However, in the conventional magnetic disk cartridge, as the write/protect tab 4 is formed greater in thickness than the height of the peripheral wall 22 of the case bottom member 2a and the projecting portions 4C, 4C are formed flat, they project upward from the side wall portions 22A, 22A in the curved wall surfaces 22C, 22C. As a consequence, when the case cover member 2b is placed upon the case bottom member 2a with the write/protect tab 4 sandwiched therebetween, the tips of the projecting portions 4C, 4C are brought into contact relation with the peripheral walls 22, 22 of the case cover member 2b as shown in FIG. 23. This contact occurs frequently in a disk cartridge in which the arm portions 4B, 4B are extended in such a manner as to be gradually dilated outwardly. However, even for a disk cartridge in which the arm portions 4B, 4B are extended not in such a fashion as discussed above, in other words, the arm portions 4b, 4b are extended substantially parallel relation, the write/protect tab 4 tends to move in the peripheral wall 22 and the projecting portions 4C, 4C are possibly frequently contacted with side wall portions. If the case cover member 2b is placed on the case bottom member 2a in that state, the contacting portions are chipped and fine powder resulting from such chipping tends to enter into the case, thus possibly resulting in error such as dropout during recording and reproducing operation.